A Montana college student whose disappearance prompted a search by hundreds of police and volunteers was found dead from injuries sustained in a car accident in the mountains of central Idaho, authorities said late on Thursday.

The body of Lucius Robbi, 21, of Orleans, California, was found in his 1997 Subaru near the remote resort town of Stanley, according to Boise County Sheriff Ben Roeber.

Robbi vanished after he set off on August 19 for the University of Montana campus in Missoula from Horseshoe Bend, Idaho, where he had worked as a guide for a second summer at a company that offers trips on the Payette River.

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Have you seen him? Lucius Robbi, 21, left Horseshoe Bend in Idaho last Tuesday but never arrived at the University of Montana. A massive search is now underway for the adventurous student

Vehicle: Robbi drove a green 1997 Subaru Legacy, pictured, and had attached two kayaks to the top

A massive search began across the Idaho wilderness for a 21-year-old student after he failed to turn up for his first day of college.

After finishing his summer job in Horseshoe Bend, Idaho last Tuesday, Lucius Robbi, packed up his car and set off for the University of Montana to arrive in time for orientation for his junior year.

The outdoor enthusiast had tied two orange kayaks to the top of his green 1997 Subaru Legacy and told relatives and friends he would drive for a while before pulling over to explore the area.

The skilled kayaker told co-workers he intended to camp out on Tuesday evening and be on hand the following day for orientation at the university.

Surveillance footage shows his car carrying kayaks as it passed a gas station in Garden Valley, Idaho about 20 minutes after he left Horseshoe Bend on Tuesday, ABC News reported.

The last ping from his cellphone was detected in the nearby town of Lowman on Tuesday afternoon - but no one heard from him after that point.

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Search efforts aided by an online campaign tied to a Facebook page called 'Finding Lucius' drew hundreds to hunt for Robbi and his Subaru across vast stretches of mountainous terrain in Idaho and Montana.

Robbi's family late on Thursday thanked law enforcement and volunteers in a post on the Facebook page, which had gathered thousands of followers from around the United States.

Location: A map shows where he was last seen in Idaho compared to his destination in Missoula, Montana

Active: Robbi, pictured, had worked in Idaho as a raft and kayak guide for the past two summers

Adventurous: Friends and relatives said he planned to camp along the route to university last week

'You were all amazing, and the overwhelming outpouring of love and the heroic effort you made to find Lucius created a bond between you and all of us that will connect us forever,' the family wrote.

The area where Idaho authorities found Robbi's remains borders the Frank Church River of No Return Wilderness and is known for whitewater rapids, rock slides, flash floods and deer and elk herds that frequently cross roadways. It has intermittent cellphone service.

A call for donations to underwrite search efforts had raised more than $18,000 on a crowd-funding website by Thursday.

Spotted: Surveillance footage outside a gas station about 20 minutes into his journey shows his car, with the kayak attached, passing by last Tuesday. His cell phone was also detected shortly afterwards

Concerns: His father Marc told ABC News that he was extremely worried about his 21-year-old son

Robbi, from Orleans, California, had worked as a guide for Cascade Raft and Kayak in Horseshoe Bend for the past two summers and enjoys other extreme sports, including snowboarding.

Before his body was found, Robbi's mother Tina Glaessner explained: 'If anyone can survive out there for seven days, he can do it.'

Kenneth Long, Robbi's supervisor at Cascade Raft and Kayak, told the Idaho Statesman that he had talked about camping along the way. His coworkers have driven along the route but have seen nothing.